Squeak Etoys is a "media authoring tool"-- software that you can download to your computer
and then use to create your own media. You can write out your project and share it with others.
Etoys runs on any Mac or Windows machine, as well as on the OLPC XO machine.
It is free.
Find out about Etoys.

Text of this guide (for searching): A Slider bar can be scripted to control other objects. Object Catalog: Slider for Remote Control. Create a drawing and a script like this one.
Get a Slider from the Object Catalog and open its Viewer. Click on basic to open the category menu for the slider.
There is a special set of tiles for the Slider. Open it. Combine tiles by joining a Slider's numeric value tile to the y value tile for the basketball.